Back Scattered Electrons (BSE) and Secondary Electrons (SE), can be emitted from a sample upon irradiation thereof by an electron beam within a microscope. Detecting BSE and SE can reveal material and surface properties of the irradiated sample. Common BSE and SE detectors include semiconductor diode detectors that produce an electric current upon an electron traversing thereon or Robinson-type detectors wherein electrons strike a scintillator layer producing photons transmitted through a light guide to a light sensor.
The semiconductor diode detector is speed limited and produces high noise and is thus less suitable for high scanning rate performance. Moreover, for SE detection, which requires operation at high voltages, use of semiconductor diode detector is undesirable. The Robinson-type detector extracts the signal via a rigid light guide through a bulky vacuum flange crowding the chamber of the microscope and imposing mechanical restrictions on the detection system. Its unidirectional light guide creates non-uniformity in the signal received from the electrons. Few light guide configurations are also possible, but impose higher complexity and cost.